Cd-vacancy and Cd-interstitial complexes in Si and Ge

The electrical field gradient (EFG), measured e.g. in perturbed angular correlation (PAC) experiments, gives particularly useful information about the interaction of probe atoms like 111In / 111Cd with other defects. The interpretation of the EFG is, however, a difficult task. This paper aims at understanding the interaction of Cd impurities with vacancies and interstitials in Si and Ge, which represents a controversial issue. We apply two complementary ab initio methods in the framework of density functional theory (DFT), (i) the all electron Korringa-Kohn-Rostoker (KKR) Greenfunction method and (ii) the Pseudopotential-Plane-Wave (PPW) method, to search for the correct local geometry. Surprisingly we find that both in Si and Ge the substitutional Cd-vacancy complex is unstable and relaxes to a split-vacancy complex with the Cd on the bond-center site. This complex has a very small EFG, allowing a unique assignment of the small measured EFGs of 54MHz in Ge and 28MHz in Si. Also, for the Cd-selfinterstitial complex we obtain a highly symmetrical split configuration with large EFGs, being in reasonable agreement with experiments

Möbius characterization of hemispheres

In this paper we generalize the Möbius characterization of metric spheres as obtained in Foertsch and Schroeder [4] to a corresponding Möbius characterization of metric hemispheres

Wiki-LDA: A Mixed-Method Approach for Effective Interest Mining on Twitter Data

Learning analytics (LA) and Educational data mining (EDM) have emerged as promising technology-enhanced learning (TEL) research areas in recent years. Both areas deal with the development of methods that harness educational data sets to support the learning process. A key area of application for LA and EDM is learner modelling. Learner modelling enables to achieve adaptive and personalized learning environments, which are able to take into account the heterogeneous needs of learners and provide them with tailored learning experience suited for their unique needs. As learning is increasingly happening in open and distributed environments beyond the classroom and access to information in these environments is mostly interest-driven, learner interests need to constitute an important learner feature to be modeled. In this paper, we focus on the interest dimension of a learner model and present Wiki-LDA as a novel method to effectively mine user’s interests in Twitter. We apply a mixed-method approach that combines Latent Dirichlet Allocation (LDA), text mining APIs, and wikipedia categories. Wiki-LDA has proven effective at the task of interest mining and classification on Twitter data, outperforming standard LDA

Maternal Environmental Contribution to Adult Sensitivity and Resistance to Obesity in Long Evans Rats

The OLETF rat is an animal model of early onset hyperphagia induced obesity, presenting multiple pre-obese characteristics during the suckling period. In the present study, we used a cross-fostering strategy to assess whether interactions with obese dams in the postnatal environment contributed to the development of obesity.On postnatal Day (PND)-1 OLETF and control LETO pups were cross-fostered to same or opposite strain dams. An independent ingestion test was performed on PND11 and a nursing test on PND18. Rats were sacrificed at weaning or on PND90, and plasma leptin, insulin, cholesterol, triglycerides and alanine aminotransferase (ALT) were assayed. Fat pads were collected and weighed and adipocyte size and number were estimated. Body weight and intake, as well as the estrous cycle of the female offspring were monitored.During the suckling period, the pups' phenotype was almost completely determined by the strain of the mother. However, pups independently ingested food according to their genotype, regardless of their actual phenotype. At adulthood, cross fostered males of both strains and LETO females were affected in regard of their adiposity levels in the direction of the foster dam. On the other hand, OLETF females showed almost no alterations in adiposity but were affected by the strain of the dams in parameters related to the metabolic syndrome. Thus, OLETF females showed reduced liver adiposity and circulating levels of ALT, while LETO females presented a disrupted estrous cycle and increased cholesterol and triglycerides in the long term.The present study provides further support for the early postnatal environment playing a sex-divergent role in programming later life phenotype. In addition, it plays a more central role in determining the functioning of mechanisms involved in energy balance that may provide protection from or sensitivity to later life obesity and pathologies related to the metabolic syndrome

Single \pi^- production in np collisions for excess energies up to 90 MeV

The quasifree reaction np\to pp\pim was studied in a kinematically complete experiment by bombarding a liquid hydrogen target with a deuteron beam of momentum 1.85 GeV/c and analyzing the data along the lines of the spectator model. In addition to the three charged ejectiles the spectator proton was also detected in the large-acceptance time-of-flight spectrometer COSY-TOF. It was identified by its momentum and flight direction thus yielding access to the Fermi motion of the bound neutron and to the effective neutron 4-momentum vector $\mathbb{P}_n$ which differed from event to event. A range of almost 90 MeV excess energy above threshold was covered. Energy dependent angular distributions, invariant mass spectra as well as fully covered Dalitz plots were deduced. Sizeable $pp$ FSI effects were found as were contributions of $p$ and $d$ partial waves. The behavior of the elementary cross section $\sigma_{01}$ close to threshold is discussed in view of new cross section data. In comparison with existing literature data the results provide a sensitive test of the spectator model.Comment: 21 pages, 9 figures, 4 tables, submitted to EPJ

Metric Möbius geometry and a characterization of spheres

We obtain a Möbius characterization of the n-dimensional spheres Sn endowed with the chordal metric d0. We show that every compact extended Ptolemy metric space with the property that every three points are contained in a circle is Möbius equivalent to (Sn, d0) for some n ≥ 1

Single-Pion Production in pp Collisions at 0.95 GeV/c (II)

The single-pion production reactions $pp\to d\pi^+$, $pp\to np\pi^+$ and $pp\to pp\pi^0$ were measured at a beam momentum of 0.95 GeV/c ($T_p \approx$ 400 MeV) using the short version of the COSY-TOF spectrometer. The central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements from other detector parts. Thus all pion production channels were recorded with 1-4 overconstraints. Main emphasis is put on the presentation and discussion of the $np\pi^+$ channel, since the results on the other channels have already been published previously. The total and differential cross sections obtained are compared to theoretical calculations. In contrast to the $pp\pi^0$ channel we find in the $np\pi^+$ channel a strong influence of the $\Delta$ excitation already at this energy close to threshold. In particular we find a $(3 cos^2\Theta + 1)$ dependence in the pion angular distribution, typical for a pure s-channel $\Delta$ excitation and identical to that observed in the $d\pi^+$ channel. Since the latter is understood by a s-channel resonance in the $^1D_2$ $pn$ partial wave, we discuss an analogous scenario for the $pn\pi^+$ channel